This invention relates generally to wellbores and wellbore casings. Wellbores are formed in subterranean formations for various purposes including the extraction of oil and gas.
When a wellbore is created, a casing is installed in the borehole to prevent collapse of the borehole wall and to prevent undesired outflow or inflow of fluid from the formation into the borehole.
When an opening is formed in the sidewalls of an existing wellbore casing, whether through damage or some other event, it is often necessary to seal off the opening. Conventional methods of sealing, such as by excavation or re-lining, are expensive and unreliable.
A cement sheath is also often used to support the casing to prevent fluids from migrating between the various zones of the wellbore. In some instances, the bond between the cement sheath and the casing fails, producing a thin annular space between the exterior surface of the casing and the cement sheath. This is often referred to as a microannulus.
The microannulus can permit fluids to migrate between zones of the subterranean formation, which can reduce the quality and efficiency of production operations. Further, a microannulus can serve as a starting point for more significant failures in the casing, including those that lead to portions of the wellbore collapsing.
The present invention is directed to overcoming one or more of the limitations of the existing procedures for repairing wellbores.
The present invention is directed to and for inhibiting, reducing, repairing or preventing the formation of a microannulus.